Positive nonsilver washout systems containing dihydropyridines and photooxidants

ABSTRACT

Process for preparation of positive images which comprises exposing imagewise a supported layer of a photosensitive composition comprising an alkali-soluble polymeric binder, at least one dihydropyridine compound and at least one hexaarylbiimidazole compound and developing by washing out the exposed image areas. Optionally auxiliary layers can be present between the support and photosensitive layer. The photosensitive elements are useful in preparing positive working printing plates and photoresists.

This is a continuation of application Ser. No. 971,663, filed Dec. 21,1978, now abandoned.

DESCRIPTION

1. Technical Field

This invention relates to new photosensitive elements, and moreparticularly to positive-working photosensitive elements.

2. Background Art

Image reproduction processes are known using photosensitive elementswherein the solubility of the photosensitive layer changes uponimagewise exposure. Depending on whether the solubility of the exposedimage areas is increased or decreased, a positive or negative imagingelement is obtained. A majority of the known image reproductionprocesses produce negative images.

One positive-working system is based on the photodecomposition ofo-quinone diazides. The photo-decomposition products occurring thereinare more soluble in aqueous alkali than are the starting compounds.

Another positive-working system is disclosed in U.S. Pat. No. 3,782,951which describes a composition of a hexaarylbiimidazole, a hydrogendonor, an ethylenically unsaturated compound, and an organic polymericbinder. In the disclosed compositions, the hexaarylbiimidazole compoundis present in a large excess above the hydrogen donor in order to attaina positive image. A double exposure process is required to achieve thepositive image. The first exposure is accomplished imagewise with highintensity radiation. After removal of the imaging master, a secondnonimage-wise exposure is accomplished with low intensity radiation. Adisadvantage of this process is that each exposure requires a differentradiation source.

Still another positive-working system is disclosed in British Pat. No.1,168,182 wherein the composition contains a hexaarylbiimidazole and aresin soluble in dilute inorganic acids. This system has a disadvantagesince the radicals which are formed as a result of the photolysis of thehexaarylbiimidazole compound produce crosslinking with the acid-solubleresins. The solubility increase effected by imagewise exposure ispartially offset by the reaction. Additionally, the presence of acidsoluble resins in the composition is disadvantageous for certain uses,for example, in photoresist applications wherein the photoresist resincoatings must withstand strong acid treatment baths for etching orplating. It has been found that acid soluble resins are inferior in thisrespect.

An object of this invention is to provide a photosensitive element forpreparing images which overcomes the above-described disadvantage.

DISCLOSURE OF INVENTION

In accordance with this invention there is provided a photosensitiveelement for the preparation of positive images which comprises a supportbearing a photosensitive layer comprising at least one alkali-solublepolymeric binder and a photosensitive system consists essentially of

I. at least one dihydropyridine compound of the formula ##STR1## whereinR is alkyl, aryl and heteroaryl,

R₁ and R₂ which can be the same or different, are alkyl, and

R₃ and R₄, which can be the same or different, are COOR', COR', CN, R'is alkyl; and

II. at least one hexaarylbiimidazole compound of the formula ##STR2##wherein the radicals A, B and D are either identical or different andare optionally substituted aryl groups derived from carbocyclic orheterocyclic compounds.

The dihydropyridine compounds can, for example, be produced according tomethods of the Hantzsch synthesis from one mol of an aliphatic oraromatic aldehyde, one mol of ammonia, and 2 mol of either aβ-ketocarbonic acid ester, a β-ketocarbonic acid nitrile, or aβ-diketone. When using β-aminocrotonic acid esters, the addition ofammonia becomes unnecessary. Other procedures are described inElderfield, Heterocyclic Compounds, Volume 1, 1950, page 462, as well asGattermann/Wieland, Die Praxis des Organischen Chemikers, 39th edition1959, page 132. Suitable dihydropyridine compounds are compiled in Table1, below. In R alkyl ranges from 1 to 11 carbon atoms, alkenyl rangesfrom 3 to 11 carbon atoms, aryl ranges from 6 to 10 carbon atoms andheteroaryl ranges from 4 to 10 carbon atoms; in R₁ and R₂ alkyl rangesfrom l to 4 carbon atoms, preferably methyl or ethyl; and in R₃ and R₄,R' is alkyl of 1 to 11 carbon atoms.

                                      TABLE 1                                     __________________________________________________________________________    COM-                                                                          POUND                                                                         I NO.                                                                              R         R.sub.1                                                                           R.sub.2                                                                           R.sub.3                                                                              R.sub.4                                         __________________________________________________________________________    1    --CH.sub.3                                                                              --CH.sub.3                                                                        --CH.sub.3                                                                        --COOCH.sub.3                                                                        --COOCH.sub.3                                   2    --CH.sub.3                                                                              --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                                 --COOC.sub.2 H.sub.5                            3    --CH.sub.3                                                                              --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.4 H.sub.9                                                                 --COOC.sub.4 H.sub.9                                                   (tert) (tert)                                          4    --CH.sub.3                                                                              --CH.sub.3                                                                        --CH.sub.3                                                                        --CN   --CN                                            5    --CH.sub.3                                                                              --CH.sub.3                                                                        --CH.sub.3                                                                        --COCH.sub.3                                                                         --COCH.sub.3                                    6    --CH.sub.3                                                                              --C.sub.2 H.sub.5                                                                 --C.sub.2 H.sub.5                                                                 -- COOC.sub.2 H.sub.5                                                                --COOC.sub.2 H.sub.5                            7    --C.sub.2 H.sub.5                                                                       --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                                 --COOC.sub.2 H.sub.5                            8    --C.sub.3 H.sub.7                                                                       --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                                 --COOC.sub.2 H.sub.5                            9    --C.sub.11 H.sub.23                                                                     --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                                 --COOC.sub.2 H.sub.5                            10   --CH.sub.2 --Phenyl                                                                     --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                                 --COOC.sub.2 H.sub.5                            11   --CH═CH--CH.sub.3                                                                   --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                                 --COOC.sub.2 H.sub.5                            12   --(CH═CH).sub.2 --CH.sub.3                                                          --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                                 --COOC.sub.2 H.sub.5                            13   --Phenyl  --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                                 --COOC.sub.2 H.sub.5                            14   --CH═CH--Phenyl                                                                     --CH.sub.3                                                                        --CH.sub.3                                                                        --COOCH.sub.3                                                                        --COOCH.sub.3                                   15   --CH═CH--Phenyl                                                                     --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                                 --COOC.sub.2 H.sub.5                            16   --CH═CH--Phenyl                                                                     --CH.sub.3                                                                        --CH.sub.3                                                                        --COOC.sub.4 H.sub.9                                                                 --COOC.sub.4 H.sub.9                            17                                                                            4-Pyridyl                                                                          --CH.sub.3                                                                              --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                              --COOC.sub.2 H.sub.5                                   18                                                                            2-Furyl                                                                            --CH.sub.3                                                                              --CH.sub.3                                                                        --COOC.sub.2 H.sub.5                                                              -- COOC.sub.2 H.sub.5                                  __________________________________________________________________________

Compounds 2, 7, 8 and 10 are preferred.

A typical procedure for producing a dihydropyridine compound (CompoundNo. 3 of Table 1 ) is described below:

In a three necked flask cooled with ice, 11.5 ml acetoaldehyde, 65 mlacetoacetic acid -tert.-butyl ester and 100 ml ethanol are mixed whilestirring, and during continued stirring and cooling, 24 ml 25% aqueousammonia solution are added dropwise. In this process the temperatureshould not exceed 35° C. After the addition is completed, stirring iscontinued for 1/2 hour and subsequently boiling takes place under refluxfor 6 hours. The dihydropyridine precipitated after cooling isrecrystallized from ethanol. Yield 38.5 g., melting point 162-163° C.

Hexaarylbiimidazole compounds are described in the German Pat. No.1,300,013 and U.S. Pat. No. 3,630,736. From the compounds mentionedthere, the hexaarylbiimidazoles disclosed in Table 2 are preferred.

                  TABLE 2                                                         ______________________________________                                        Com-                                                                          pound                                                                         II No.                                                                              A             B             D                                           ______________________________________                                        Phenyl                                                                        Phenyl                                                                        Phenyl                                                                        2                                                                             2-Chlorophenyl                                                                Phenyl                                                                        Phenyl                                                                        3                                                                             2-Chlorophenyl                                                                3-Methoxyphenyl                                                               3-Methoxy-                                                                                                      phenyl                                      4                                                                             2-Methoxyphenyl                                                               Phenyl                                                                        Phenyl                                                                        ______________________________________                                    

Components I and II, described above, contained in the photosensitivelayer can fluctuate within broad limits depending on the use. Amountranges which lead to especially good results are 5 to 30% by weightdihydropyridine Compound I and 10 to 50% by weight hexaarylbiimidazoleCompound II based on the total weight of the photosensitive composition.

To prepare the photosensitive elements, the photosensitive compositioncomprised of dihydropyridine and hexaarylbiimidazole components with atleast a known compatible organic alkali-soluble polymer binder isapplied to a support by a procedure as described below. A large numberof alkali soluble binders are known, e.g., acrylic acid and/ormethacrylic acid polymers and/or their copolymers with other suitablemonomers, e.g., acrylic acid esters or other acryl derivatives, vinylcompounds such as vinyl ethers, vinyl acetates or their saponificationproducts, styrene, vinyl pyrrolidone, butadiene and related monomers;copolymers of maleic acid anhydride, maleic acid, maleic acid halfesters, maleic acid, half amides and derivatives of relates compounds,e.g., itaconic acid, with suitable comonomers, e.g., styrene, ethylene,vinyl acetate, etc; polystyrene sulfonic acids and/or their copolymers;cellulose derivatives, e.g., carboxymethyl cellulose, cellulosephthalate or cellulose succinate; alginic acids and their derivatives.Additionally, phenol-formaldehyde resins, known under the designationNovolac® are suitable.

Copolymers of maleic acid anhydride or maleic acid half esters withstyrene have proven to be especially advantageous binders for theproduction of the photosensitive elements. The concentration of thepolymeric binder is about 20 to 80% by weight based on the total weightof the photosensitive composition.

In addition to the mentioned components, the photosensitive layers canoptionally contain further additives in amounts known to those skilledin the art, e.g., sensitizers, stabilizers, dyes, pigments, delusteringagents, softeners, auxiliary coating agents, etc. Michler's ketone ispreferred as a sensitizer.

A large number of transparent or opaque materials can be used as asupport for the photosensitive layers, e.g., paper, optionally treatedwith barite; cardboard; metal foils, e.g., aluminum, copper, steel,etc.; wood; glass; foils or fiber webs of natural or synthetic polymers,e.g., polyamides, rubber, polyethylene or polypropylene, linearpolyesters, e.g., polyethylene terephthalate; cellulose, celluloseesters, polyvinly chloride or their copolymers, polyacrylonitrile, etc.

A special protective film present over the photosensitive layer whichmust be removed before the development procedure is generally notnecessary. It can, however, if desired, be present to prevent damage tothe photosensitive coating. If necessary, it is also possible to applyadditional nonphotosensitive coatings to the support, for example, anantihalation coating.

The components of the photosensitive layer are generally deposited as asolution in volatile solvents according to well-known methods andsubsequently dried. Suitable solvents are, for example, methylenechloride, acetic acid ethylester, acetone, etc. Other depositing methodswithout the use of solvents such as calendering, extruding or the likeare also useful.

The concentration of the nonvolatile components of the coating solutioncan fluctuate within broad limits but is dependent on the coating methodand the layer or relief thickness desired for the different purposes ofapplication.

For the production of the images, the photo-sensitive element is exposedwith radiation sources which emit a radiation rich in ultraviolet light,for example, mercury vapor lamps, xenon lamps, etc. through a mastercopy. The exposed image areas are then developed by washing out theexposed areas of the image. For this development process, preferablyaqueous alkaline solutions are used which can contain, for example, assuitable alkalis alkali-carbonates, borates and alkalihydroxides as wellas the well-known carbonate, borate and phosphate buffer systems. Thedevelopment solutions can, furthermore, contain surface activesubstances.

BEST MODE FOR CARRYING OUT THE INVENTION

The best mode is illustrated in Example 3 wherein the photosensitiveelement contains a photo-sensitive layer containing styrene/maleicanhydride binder and Compounds 2 from each of Tables 1 and 2.

INDUSTRIAL APPLICABILITY

The photosensitive elements are useful for a number of purposesincluding positive working printing plates of diverse kinds, e.g., foroffset printing or relief printing; positive working photoresist layers,e.g., for the production of printed circuits; or copying films for theproduction of positive contact copies. In the latter case, thephotosensitive layers contain dyes or pigments. In a special embodimentfor the production of copying films, the dye or pigment present in thephotosensitive layer can be entirely or partially located in a separatelayer between the support and the photosensitive layer.

EXAMPLES

The following examples illustrate the invention.

EXAMPLE 1

A coating solution of the following composition is prepared:

10 g phenolformaldehyde resin (Alnovol®)

2 g of Compound 3 of Table 1

2 g of Compound 3 of Table 2

0.2 g of a blue triaryl methane dye (Victoria Pure Blue® FGA) (CI BasicBlue 81)

75 ml methylene chloride/acetone (9:1 by volume)

The solution is applied to an aluminum plate as is used for theproduction of offset printing plates. The plate is then exposed througha master copy for 120 seconds with a mercury vapor lamp (1,000 watts) ata distance of 60 cm. Subsequently, the plate is developed with anaqueous 0.2 standard NaOH solution (90 seconds, 20° C.) and rinsed withwater whereby the exposed image portions are washed out. A positiveworking offset printing plate with a high useful life is obtained.

EXAMPLE 2

A coating solution of the following composition is prepared:

10 g copolymer acrylic acid ethylester/methacrylic acidmethylester/acrylic acid (55/40/5 mol%), average molecular weight260,000

4 g of the Compound 17 of Table 1

4 g of the Compound 2 of Table 2 0.5 g of Michler's ketone

75 ml methylene chloride/acetone (9:1 by volume)

The solution is applied to an aluminum plate as is used for theproduction of offset printing plates. The plate is then exposed througha master copy for 90 seconds with a mercury vapor lamp (1,000 watts) ata distance of 60 cm. Subsequently, the plate is treated with a solutionof the following composition (80 seconds, 25° C.):

2 g potassium carbonate

1 g potassium hydrogen carbonate

97 g water

and is then rinsed with water whereby the exposed image portions arewashed out. A positive working offset printing plate with a high usefullife is obtained.

EXAMPLE 3

A coating solution of the following composition is prepared:

3.5 g copolymer styrene/maleic acid anhydride (50/50 mol %)

1.0 g copolymer acrylic acid ethylester/methacrylic acidmethylester/acrylic acid (55/40/15 mol %), average molecular weight26,000

1.5 g of Compound 2 to Table 1

3.5 g of Compound 2 of Table 2

1.0 polyethylene oxide, average molecular weight, 1,500

75 ml methylene chloride/methanol (9:1 by volume)

The solution is applied to a polyethylene glycol terephthalate filmsupport.

This material is laminated with the coating side on a copper printedcircuit board as is used for the production of printed circuits andexposed behind a master copy for 60 seconds with a mercury vapor lamp(1,000 watts) at a distance of 80 cm. After removing the polyester film,the plate is treated with a solution of the following composition:

2 g potassium carbonate

1 g potassium hydrogen carbonate

and is then sprayed with water whereby the exposed image portions areremoved. The plate is subsequently etched in a known manner with anaqueous ferrichloride solution of 48° Be and the remaining resist layeris removed by treating it with a 0.5 standard caustic soda solution. Apositive metallic conductive circuit image is obtained.

EXAMPLE 4

A coating solution of the following composition is prepared:

9.5 g copolymer acrylic acid ethylester/methacrylic acidmethylester/acrylic acid (55/40/5 mol %), average molecular weight26,000

7.0 g copolymer styrene/maleic acid anhydride (50/50 mol %)

4.0 g of the Compound 2 of Table 1

4.0 g of the Compound 2 of Table 2

2.5 g carbon pigment

75 ml methylene chloride

The solution is applied to a substrate of polyethylene glycolterephthalate. The film is then exposed through a line or screen mastercopy for 50 seconds with a mercury vapor lamp (1,000 watts) at adistance of 80 cm. Subsequently, the film is developed with a solutionof the following composition (25 seconds, 35° C.):

2.8 g potassium carbonate

0.6 g potassium hydrogen carbonate

96.6 g water

and is then sprayed with water whereby the exposed image areas arewashed out. A positive black and white copy of the master copy used isobtained.

EXAMPLE 5

A coating solution of the following composition is prepared:

25 g partially esterified copolymer styrene/maleic acid anhydride (50/50mol %), available as SMA 17,352 from the ARCO Chem. Co.

5 g of the Compound 1 of Table 1

10 g of the Compound 4 of Table 2

100 ml acetone

The solution is applied to a polypropylene substrate. This film islaminated with the coating side on a dry coating, half consisting of apartially esterified styrene/maleic acid anhydride copolymer and half ofa black dye "Zaponechtschwarz RE", which is present on a polyethyleneterephthalate substrate.

This material is exposed through the polypropylene film through a lineor screen master copy for 120 seconds with a mercury vapor lamp (1,000watts) at a distance of 80 cm. Subsequently, the film is developed afterremoval of the polypropylene film with a solution of the followingcomposition (30 seconds, 20° C.):

1.5 g sodium carbonate (water-free)

0.5 g sodium hydrogen carbonate

98.0 g water

and subsequently rinsed with water whereby the photosensitive layer aswell as the black coating under it are washed out at the exposed imagelocations. A positive black and white copy of the master copy used isobtained.

We claim:
 1. A process for the preparation of positive images whichcomprises exposing imagewise to actinic radiation a photosensitiveelement which comprises a support bearing a photosensitive layercomprising at least one alkali-soluble polymeric binder and aphotosensitive system consisting essentially ofI. at least onedihydropyridine compound of the formula ##STR3## wherein R is alkyl,alkenyl of 3 to 11 carbon atoms, phenyalkyl, phenylalkenyl,unsubstituted aryl of 6 to 10 carbon atoms and unsubstituted heteroaryl,R₁ and R₂, which can be the same or different, are alkyl, and R₃ and R₄,which can be the same or different, are COOR', COR', CN, R' is alkyl;andII. at least one hexaarylbiimidazole compound of the formula ##STR4##wherein the radicals A, B and D are either identical or different andare optionally substituted aryl groups derived from carbocyclic orheterocyclic compounds, and developing by washing out the exposed areasof the image.
 2. A process according to claim 1 wherein thedihydropyridine compound is2,4,6-trimethyl-3,5-bis(carbethoxy)-1,4-dihydropyridine.
 3. A processaccording to claim 1 wherein the dihydropyridine compound is2,6-dimethyl-4-ethyl-3,5-bis(carbethoxy)-1,4-dihydropyridine.
 4. Aprocess according to claim 1 wherein the dihydropyridine compound is2,6-dimethyl-4-n-propyl-3,5-bis(carbethoxy)-1,4-dihydropyridine.
 5. Aprocess according to claim 1 wherein the dihydropyridine compound is2,6-dimethyl-4-benzyl-3,5-bis(carbethoxy)-1,4-dihydropyridine.
 6. Aprocess according to claim 1 wherein the hexaarylbiimidazole compound is2,2',4,4',5,5'-hexaphenylbiimidazole.
 7. A process according to claim 1wherein the hexaarylbiimidazole compound is2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole.
 8. A processaccording to claim 1 wherein the hexaarylbiimidazole compound is2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetrakis(3-methoxyphenyl)biimidazole.9. A process according to claim 1 wherein the hexaarylbiimidazolecompound is 2,2'-bis(2-methoxyphenyl)-4,4'5,5'-tetraphenylbiimidazole.10. A process according to claim 1 wherein a sensitizer is present inthe photosensitive layer.
 11. A process according to claim 10 whereinthe sensitizer is Michler's ketone.
 12. A process according to claim 1wherein a dye or pigment is present in the photosensitive layer.
 13. Aprocess according to claim 1 wherein a dye or pigment is at leastpartially present in a nonphotosensitive auxiliary layer present betweenthe support and the photosensitive layer.
 14. A process according toclaim 1 wherein the exposed areas of the image are washed out with anaqueous alkaline solution.